1. Field of the Invention
The present invention relates to a solid-state imaging device with an optical waveguide on a light receiving unit and also relates to an imaging apparatus provided with such a solid-state imaging device.
2. Description of the Related Art
In a solid-state imaging device, the more the distance from the center of the imaging device to a pixel increases, the more the incident angle of light on the pixel increases. Thus, the amount of light incident on the photoelectric conversion unit (light receiving unit) decreases if the uppermost lens is located just above a photoelectric conversion unit (light receiving unit).
Then, there is proposed a solid-state imaging device in which the horizontal position of each of the lens and the photoelectric conversion unit (light receiving unit) is shifted depending on the distance from the center of the imaging device to the pixel to place the lens near the center of the imaging device (see, for example, Japanese Patent Laid Open Nos. 2006-261247, 2006-261249, and 2006-324439). Such a configuration of the imaging device can allows the more amount of the slanting incident light passed through the lens to enter the photoelectric conversion unit (light receiving unit), resulting in sufficient sensitivity. The shifting of the horizontal positions of structural components, such as a lens and a light receiving unit, in this way is referred to as “pupil correction”. In other words, the term “pupil correction” means that an on-chip lens is shifted to an appropriate position to take measures against a fact that the incident light is not vertically incident on the periphery of a pixel but obliquely incident thereon.
In Japanese Patent Laid Open No. 2006-261249, furthermore, an optical waveguide is provided between a lens and a light receiving unit. Then, the lens, the optical waveguide, and the light receiving unit are shifted in the horizontal direction so that the distances from the center of the imaging device to the lens, the optical waveguide, and the light receiving unit increase in this order with an increase in distance from the center of the imaging device to the pixel.
By the way, in the typical CMOS type solid-stage imaging device, a transistor and a floating diffusion are provided for every pixel. The presence of the transistor and the floating diffusion in each pixel restricts the production of a finer pixel. The finer the pixel is made, the more the surface area of the light receiving unit decreases. As a result, a decrease in amount of electric charges occurs. Thus, the resulting pixel may tend to be a very dark pixel and also random noise may tend to overlap an image signal.
To avoid such phenomena, there is proposed another imaging device in which a transistor and a floating diffusion are shared by two or more pixels to decrease the surface area of the pixel occupied by these elements while increasing the surface area thereof occupied by the light receiving unit (see, for example, Japanese Patent Laid Open No. 2006-303468).